<!DOCTYPE html>
<html>
    <head lang="en">
        <script type="text/javascript" src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    </head>
    <body>
       <div id="app-3">
           <p v-if="seen">现在看到我了</p>
       </div>
       <div id="app-4">
        <ol>
          <li v-for="todo in todos">
            {{ todo.text }}
          </li>
        </ol>
      </div>

       <script type="text/javascript">
            var app3 =new Vue({
                el:'#app-3',
                data:{
                    seen:true
                }
            });

            var app4 = new Vue({
                    el: '#app-4',
                    data: {
                    todos: [
                    { text: '学习 JavaScript' },
                    { text: '学习 Vue' },
                    { text: '整个牛项目' }
                    ]
                     }
                });
        </script>        
    </body>
</html>